JULIO CESAR M. DA SILVA
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Artigo IPEN-doc 20451 Palladium and palladium-tin supported on multi wall carbon nanotubes or carbon for alkaline direct ethanol fuel cell2015 - GERALDES, ADRIANA N.; SILVA, DIONISIO F. da; SILVA, JULIO C.M. da; SA, OSVALDO A. de; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIRPd and PdSn (Pd:Sn atomic ratios of 90:10), supported on Multi Wall Carbon Nanotubes (MWCNT) or Carbon (C), are prepared by an electron beam irradiation reduction method. The obtained materials are characterized by X-Ray diffraction (XRD), Energy dispersive X-ray analysis (EDX), Transmission electron Microscopy (TEM) and Cyclic Voltammetry (CV). The activity for ethanol electro-oxidation is tested in alkaline medium, at room temperature, using Cyclic Voltammetry and Chronoamperometry (CA) and in a single alkaline direct ethanol fuel cell (ADEFC), in the temperature range of 60e90 C. CV analysis finds that Pd/MWCNT and PdSn/MWCNT presents onset potentials changing to negative values and high current values, compared to Pd/C and PdSn/C electrocatalysts. ATR-FTIR analysis, performed during the CV, identifies acetate and acetaldehyde as principal products formed during the ethanol electrooxidation, with low conversion to CO2. In single fuel cell tests, at 85 C, using 2.0 mol L 1 ethanol in 2.0 mol L 1 KOH solutions, the electrocatalysts supported on MWCNT, also, show higher power densities, compared to the materials supported on carbon: PdSn/MWCNT, presents the best result (36 mW cm 2 ). The results show that the use of MWCNT, instead of carbon, as support, plus the addition of small amounts of Sn to Pd, improves the electrocatalytic activity for Ethanol Oxidation Reaction (EOR).Artigo IPEN-doc 20049 Investigation of PdIr/C electrocatalysts as anode on the performance of direct ammonia fuel cell2014 - ASSUMPCAO, M.H.M.T.; SILVA, S.G. da; SOUZA, R.F.B. de; BUZZO, G.S.; SPINACE, E.V.; SANTOS, M.C.; NETO, A.O.; SILVA, J.C.M.This work investigates the ammonia electro-oxidation considering electrochemical and direct ammonia fuel cell (DAFC) experiments. The working electrodes/anodes are composed of Pd/C, PdIr/C (90:10, 70:30, 50:50, 30:70 and 10:90 atomic ratios) and Ir/C. Solutions of 1 mol L1 NH4OH and 1 mol L1 KOH were used for electrochemical experiments while 1.0, 3.0 and 5.0 mol L1 NH4OH in 1.0 mol L1 KOH were used in DAFC. X-ray diffraction analysis of PdIr/C electrocatalysts suggests the formation of PdIr alloy, while transmission electron micrographs show the average particle diameters between 4.6 and 6.2 nm. Electrochemical experiments indicate PdIr/C 30:70 as the best electrocatalyst in accordance with DAFC. The maximum power densities obtained with PdIr/C 30:70 as anode using 5 mol L1 NH4OH and 1 mol L1 KOH at 40 C are 60% and 30% higher than the ones obtained with Pd/C and Ir/C electrocatalysts, respectively. The enhanced synergic effect in this specific composition may be assigned to an optimal ratio of palladium sites that dehydrogenates ammonia at lower overpotential with the lower surface coverage of Nads on iridium. Furthermore, electronic effect between palladium and iridium might also contribute to the decrease of poisoning on catalyst surface by Nads.Artigo IPEN-doc 19961 The effect of ethanol concentration on the direct ethanol fuel cell performance and products distribution2014 - ASSUMPCAO, M.H.M.T.; NANDENHA, J.; BUZZO, G.S.; SILVA, J.C.M.; SPINACE, E.V.; OLIVEIRA NETO, A.; SOUZA, R.F.B.The effect of ethanol concentration on the direct ethanol fuel cell (DEFC) performance and products distribution were studied in situ using a single fuel cell/ATR-FTIR setup. The experiments were performed at 80 C using commercial Pt3Sn/C as anodic catalyst and the concentrations of ethanol solution were varied from 0.1 to 2.0 mol L1 . An increase in power density was observed with the increase of ethanol concentration to 1.0 mol L1 , while the band intensities analysis in the FTIR spectra revealed an increase of acetic acid/acetaldehyde ratio with the increase of ethanol concentration. Also, from FTIR spectra results, it could be concluded that the acetic acid production follow parallel mechanisms; that is, it does not require the presence of acetaldehyde as an intermediate.Artigo IPEN-doc 12672 Study of ethanol electro-oxidation in acid environment on Ptsub(3)Sn/C anode catalysts prepared by a modified polymeric precursor method under controlled synthesis conditions2010 - SOUZA, R.F.B. de; PARREIRA, L.S.; RASCIO, D.C.; SILVA, J.C.M.; TEIXEIRA NETO, E.; CALEGARO, M.L.; SPINACE, E.V.; OLIVEIRA NETO, A.; SANTOS, M.C.